nav {
    background-image: url(../img/banner.png);
    background-position: center center;
    background-size: cover;
}

.introduction1 {
    background-image: url(../img/kai-fa.png);
    width: 100vw;
    height: 50vh;
    background-position: center center;
    background-size: cover;
}

.introduction2 {
    background-image: url(../img/gong-guan.png);
    width: 100vw;
    height: 50vh;
    background-position: center center;
    background-size: cover;
}

.introduction3 {
    background-image: url(../img/zu-zhi.png);
    width: 100vw;
    height: 50vh;
    background-position: center center;
    background-size: cover;
}

.introduction4 {
    background-image: url(../img/nei-wu.png);
    width: 100vw;
    height: 50vh;
    background-position: center center;
    background-size: cover;
}

.study1 {
    display: flex;
    align-items: center;
    background-image: url(../img/UI设计.png);
    background-repeat: no-repeat;
    background-position: right center;
    background-size: 28%;
    height: 40vh;
    /* margin-top: 5vh; */
    padding: 2vh 0;
}

.study2 {
    background-image: url(../img/前端开发.png);
    background-repeat: no-repeat;
    background-position: left center;
    background-size: 28%;
    height: 40vh;
    /* margin-top: 5vh; */
    display: flex;
    align-items: center;
    padding: 2vh 0;
    flex-direction: row-reverse;
}

.study3 {
    background-image: url(../img/后端开发.png);
    background-repeat: no-repeat;
    background-position: right center;
    background-size: 28%;
    height: 40vh;
    /* margin-top: 5vh; */
    padding: 2vh;
    display: flex;
    align-items: center;
    padding: 2vh 0;
}

.study4 {
    background-image: url(../img/网络技术.png);
    background-repeat: no-repeat;
    background-position: left center;
    background-size: 28%;
    height: 40vh;
    /* margin-top: 5vh; */
    display: flex;
    align-items: center;
    padding: 2vh 0;
    flex-direction: row-reverse;
}

.study5 {
    background-image: url(../img/移动开发.png);
    background-repeat: no-repeat;
    background-position: right center;
    background-size: 28%;
    height: 40vh;
    /* margin-top: 5vh; */
    display: flex;
    align-items: center;
    padding: 2vh 0;
}